1. Field of the Invention
The present invention relates to a location information system based on SUPL (Secure User Plane Location) technology, and more particularly, to a SUPL initiation message for initiating a SUPL procedure for checking a location and a method and a system for providing the SUPL by using the SUPL initiation message.
2. Description of the Related Art
In general, a mobile communication system has a function part for calculating a location of a terminal in a mobile communication network to provide a location service that transfers the location of the terminal to a certain entity in a periodic manner or according to a corresponding request.
A network structure related to the location service differs depending on an internal structure of a particular network such as a 3GPP network, a 3GPP2 network, etc. According to the related art, there are several methods for calculating the position (location) of a mobile terminal, including a cell-ID method for transferring an ID of a cell to which a mobile terminal belongs, a method for calculating a location of a mobile terminal through triangulation by measuring the time required for radio signals to reach each base station from the mobile terminal, and a method of using GPS (Global Positioning System) technology.
In order to provide the location service to a user, a large quantity (amount) of signals and location information are to be transferred between the mobile terminal and a location server. Recently, positioning technologies for providing the location service (namely, location services provided based on a location of a mobile terminal) are increasingly used. These technologies can be provided generally through a user plane and a control plane, one of which is a SUPL (Secure User Plane Location) technique that provides the location service through the user plane.
As an effective method for transferring location information required for calculating a location of the mobile terminal, the SUPL (Secure User Plane Location) uses a user plane data bearer to transfer location assistance information such as GPS assistance and transferring a positioning technology-related protocol between the mobile terminal and a network.
Generally, in the location information system, the SUPL network related to the location service includes a SUPL agent, an SLP (SUPL location platform) and a SET (SUPL Enabled Terminal), etc. The SUPL agent is a logical service access point (AP) using actually measured location information, and the SLP is a SUPL service AP of a network part that accesses network resources to obtain the location information. The SET is a device for communicating with the SUPL network using a SUPL interface, which supports definition procedures in the SUPL by interworking with the network through a user plane data bearer. In this case, the SET can be one of a UE (User Equipment) for UMTS, an MS (mobile Station) for GSM, and a laptop computer or a PDA (Personal Digital Assistant) having the SET function. Alternatively, the SET can refer to various types of mobile terminals connected through the WLAN.
In the location information service, a network to which the user has originally registered is called a home network, and a network of an area to which the user is located after having moved from the home network is called a visited network. An SLP within the home network is called a home SLP (H-SLP), and an SLP within the visited network is called a visited SLP (V-SLP).
When the SUPL procedure is started in the network of the location information system, an SLP first connected by an external client is called a requesting SLP (R-SLP), which is a logical entity that may or may not be the same as the H-SLP. A SET aimed for tracking current location is called a target SET.
The SLP, a network element, generally includes an SPC (SUPL Positioning Center) that calculates actual location information and an SLC (SUPL Location Center) that handles additional functions other than calculating the location information. For example, the SLC performs and/or supports the procedures for roaming, resource management, and the like.
The location information system can be implemented in a non-proxy mode in which the SPC has direct communication with the SET to calculate the location information, and in a proxy mode in which the SPC does not have direct communication with the SET but communicates with the SET via the SLC to calculate the location information. In the proxy mode environment, the SLC operates as a proxy between the SET and SPC.
In the general SUPL-based location information system, an address of the SLP that may be connected by the terminal (SET) to perform the SUPL procedure, can be an IP address based on IPv4 or IPv6 or a URL (Uniform Resource Locator). In case of roaming, the SLP address can be an address of the H-SLP or an address of the V-SPC.
Upon receiving the SLP address, e.g., in a non-proxy mode, the terminal can perform the steps of checking the IP address of the URL included in the SLP address, connecting with the SLP corresponding to the address, opening a session with the corresponding SLP, and performing the SUPL procedure. In this case, in the SUPL procedure of the home network, the SLP to which the terminal is connected is the H-SLP, while in case of roaming, the terminal existing in the visited network should be connected with the V-SLP. The address of the SLP to which the terminal is to be connected may differ depending upon whether the SLP is in the proxy mode or the non-proxy mode.
However, in the general SUPL-based location information system, the SLP address itself does not and cannot be used to discriminate whether it is the address of the H-SLP or the V-SPC, e.g., in case of roaming. As a result, this causes a problem in that the terminal which has received the SLP address cannot accurately determine the particular server to which the terminal should be connected for performing the SUPL procedure and thus may not be able to perform subsequent set-up and other operations effectively. That is, since different steps may need to be taken to perform the SUPL procedure depending on whether the system is in a proxy mode or a non-proxy mode, just receiving an SLP address is not enough for the terminal to know in what capacity the SLP address should be used.
In addition, in the general SUPL-based location information system, in case of non-proxy roaming, the terminal, which has received a SUPL initiation message containing an SLP address, cannot discriminate (1) whether to be connected directly to the V-SPC by using the SLP address (which is the V-SPC address) included in the SUPL initiation message or (2) whether to open a session with the H-SLP, receive an authentication key, and then connect with the V-SPC using the SLP address included in the SUPL initiation message. Additionally, the network part cannot properly inform the terminal about what it should do.